Engine torque and torque converter bypass clutch slip control during vehicle launch

Abstract

A method of operating a vehicle includes, responsive to a command to launch the vehicle and while the vehicle is in a first gear, determining, at a controller, a feedforward component including a target engine torque and a target bypass clutch torque, and a feedback component that is based on an error between the target converter slip and a measured converter slip and between the target wheel torque and a measured wheel torque. The method further includes changing a commanded engine torque and a commanded bypass clutch torque based on the feedforward component and the feedback component.

What is claimed is: 
     
       1. A vehicle comprising:
 an engine including a crankshaft; 
 a transmission including a torque converter having an impeller, and a turbine fixed to a turbine shaft that is driveably connected to driven wheels of the vehicle, wherein the torque converter further includes a bypass clutch configured to selectively lock the impeller and turbine relative to each other; 
 a speed sensor disposed within the transmission and configured to output a speed signal indicating a measured impeller speed; 
 a bypass clutch configured to output a slip signal indicating a slip at the bypass clutch; and 
 at least one controller configured to, in response to a command to launch the vehicle and while the vehicle is in a first gear,
 determine a feedforward component including a target converter slip and a target bypass clutch torque, 
 determine a feedback component that is based on an error between a target converter slip and a measured converter slip and between a target wheel torque and a measured wheel torque, and 
 change a commanded engine torque and a commanded bypass clutch torque based on the feedforward component and the feedback component. 
 
 
     
     
       2. The vehicle of  claim 1  wherein the controller is further configured to modify the target wheel torque to a clipped target wheel torque responsive to the engine being unable to deliver the target wheel torque. 
     
     
       3. The vehicle of  claim 1  wherein the controller is further configured to modify the target converter slip to a clipped converter slip responsive to the target converter slip exceeding an open converter slip. 
     
     
       4. The vehicle of  claim 1  wherein the determination of the feedforward component and the feedback component are adjacent in time to each other. 
     
     
       5. The vehicle of  claim 1  wherein the crankshaft of the engine is selectively coupled with the bypass clutch. 
     
     
       6. The vehicle of  claim 1  wherein the command to launch the vehicle is received while a speed of the vehicle is zero. 
     
     
       7. The vehicle of  claim 1  wherein the command to launch the vehicle is responsive to a change in pedal position of a brake pedal. 
     
     
       8. The vehicle of  claim 1  wherein the command to launch the vehicle is responsive to a change in pedal position of an accelerator pedal. 
     
     
       9. The vehicle of  claim 1  further comprising an electric machine including a rotor selectively coupled to the crankshaft. 
     
     
       10. The vehicle of  claim 9  further comprising a disconnect clutch that selectively couples the crankshaft to the rotor of the electric machine. 
     
     
       11. The vehicle of  claim 1  wherein the impeller is fixed to a crankshaft of the engine and the turbine is disposed on an input shaft of the transmission. 
     
     
       12. A method of operating a vehicle comprising:
 responsive to a command to launch the vehicle, at a controller:
 determining a feedforward component including a target engine torque and a target bypass clutch torque, and a feedback component that is based on an error between a target converter slip and a measured converter slip and between a target wheel torque and a measured wheel torque; and 
 changing a commanded engine torque and a commanded bypass clutch torque based on the feedforward component and the feedback component. 
 
 
     
     
       13. The method of  claim 12  further comprising:
 at the controller, modifying the target wheel torque to a clipped target wheel torque responsive to the engine being unable to deliver the target wheel torque. 
 
     
     
       14. The method of  claim 12  further comprising:
 at the controller, modifying the target converter slip to a clipped converter slip responsive to the target converter slip exceeding an open converter slip. 
 
     
     
       15. The method of  claim 12  wherein the determination of the feedforward component and the feedback component are adjacent in time to each other. 
     
     
       16. The method of  claim 12  further comprising generating a command to start an engine. 
     
     
       17. The method of  claim 12  wherein the command to launch the vehicle is received while the vehicle is in a first gear. 
     
     
       18. The method of  claim 12  wherein the command to launch the vehicle is received while a speed of the vehicle is zero. 
     
     
       19. The method of  claim 12  wherein the command to launch the vehicle is responsive to a change in pedal position of a brake pedal. 
     
     
       20. A method comprising:
 responsive to a command to launch a vehicle, at a controller:
 changing a commanded engine torque and a commanded bypass clutch torque based on 
 a feedforward component that includes a target engine torque and a target bypass clutch torque, and 
 a feedback component that is based on an error between a target converter slip and a measured converter slip and between a target wheel torque and a measured wheel torque.